NGUdi HldNG DAN KHOA HOC:
PGS. TS. PHAM QUOC TRIEU
LOI CAM ON
Toi xin chan thanh cam on su giiip do cua PGS. TS. Pham Qu6c Trieu, nguai da tan tinh huang din de toi hoan thanh duge cu6n luan van naỵ Toi ciing xin cam on su giiip da chi bao va dong g6p y ki^n ciia GS. TS. Vii Anh Phi va PGS. TS. Hoang Nam Nhat
Trong qua trinh lam luan van toi da nhan duge sir giiip da nhiet tinh ciia cac d6ng nghiep tai khoa Vat ly nhu: ThS. D6 Trung Kien, ThS. Trin VTnh Thdng va ThS. Nguyen Ngpc Dinh.
Toi cung xin cam an toan bp thay co trong trong khoa Vat ly va dac biet la cac thay co trong Bp mon Vat ly Vo tuyen da trang bi cho toi ve mat kien thiic trong suot qua trinh hpc tap va lam viec a day, cung nhu tao moi dieu kien thuan Igi de toi hoan thanh cuon luan van naỵ
Cuoi cung toi xin cam on tai gia dinh va ban be da luon dong vien, khich le tinh than de toi hoan thanh ban khoa luan naỵ
Hd noi, thang 12 nam 2006
M d D A U 1
CHUONG I L K H U E C H DAI LOCK-IN 2
1.1 Giai thieu chung 2 1.2 Cac khai niem ca ban 3
1.2.1 Kenh tin hieu (The signal channel) 3
1.2.2 Bg tach song dong bp 4 1.2.2.1 Giai dieu che voi tin hieu chuan dong bp (Demodulation with
a synchronous reference) 5 1.2.2.2 Giai dieu che bien dp (amplitude demodulation) 6
1.2.2.3 Giai dieu che pha (phase demodulation) 7 1.2.2.4 Dieu che trpn (Mixed modulations) 8 1.3 Bp phat hien nhay pha (Phase-sensitive detection) 8
1.3.1 Giai thieu 8 1.3.2 Nguyen ly boat dong 9
1.3.3 Cac khai niem lien quan den bp PSD 13
1.3.3.1 Dp nhay Full-scale 13 1.3.3.2 Dynamic reserve 13 1.4 Khu6ch dai lock-in hai pha (Two-phase Lock-in amplifier) 14
1.5 Cac nguon nhieu 16 1.5.1 Cac ngu6n nhilu noi (Intrinsic noise sources) 16
1.5.1.1 Nhilu Johnson 16 1.5.1.2 Shot noise ^17 1.5.1.2 Nhieu 1/f 17 1.5.2 Cac ngu6n nhieu ngoai (External noise sources) 17
1.5.2.2 Lien ket cam ung 19
1.5.2.3 Lien k€t dien tra 20
1.5.2.4 Dao dgngcahgc 20
CHUONG IILCO SCJ DSP (DIGITAL SIGNAL PROCESSING) 22
2.1 Lay mau (Sampling) 22 2.1.1 Giai thieu 22 2.1.2 Bien d6i tuang tu - s6 (A/D) 22
2.1.2.1 Lay mlu tuan hoan 23 2.1.2.2. Lugng tii h6a va ma h6a 26 2.1.3 Bien doi so thanh tuang tu 27
2.2.1 Bp loc (Filters) 30 2.2.1.1 Giai thieu cac bg Igc s6 (Digital filter) 30
2.2.1.2 Bp loc ly tuang 31 2.2.1.3 Bp Ipc thuc te (Nonideal Filters) 32
2.2.1.4 Bg Igc IIRva FIR 35 2.2.1.4.1 Bp loc CO dap ling xung vo han IIR 36
2.2.1.4.2 Bp Ipc c6 dap ling xung hiju ban FIR (Finite Impulse
Response Filter) 41 (adsbygoogle = window.adsbygoogle || []).push({});
CHUONG I I I L X A Y DUNG HE KFIUECH DAI LOCK-IN SO 43
Sir DUNG MAY TINH 43
3.1 Giai thieu 43 3.2 Xay dung khuach dai lock-in s6 44
3.2.1 So d6 kh6i va nguyen t^c lam viec ciia khuech dai lock-in hai pha 45
3.2.2 Phln Cling 46 3.2.2.1 TSng tien khuSch dai 46
3.2.2.2 Card am thanh 47
3.2.3 Ph§n mem 51
3.2.3.1 Tin hieu chuan (reference signal) 51
3.2.3.2 Bo nhan 53 3.2.3.3 Bo loc 55 3.2.3.4 Do bien do vapha 56
CHUONG IV: KET QUA VA THAO LUAN 58
4.1 Khao sat 59 4.2 Cac ling dung 65
4.2.1 Do he so tu hoa dong 65 4.2.2 Cau can bang AC 66 4.2.3 Do tra khang AC 68 4.2.4 Xay dung bai thuc tap ve khuech dai lock-in so 70
4.3 Cac han che 71
KET LUAN 72 TAI LIEU THAM KHAO 73